Well, there is a way to close the .Jar file, it's a bit complicated though! (not really

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To Close it after it's ran (trust me on this, i've had to do it a number of times) You go into (for windows) Your Windows Task Manager (ctrl + alt then hit delete) and choose the program and click End Now.
You'll get a message saying (for windows) "This Program is not Responding" Just click End Now and wait about 2-4 minutes, and there ya go

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